1. Field of the Invention
The present invention relates to a format overlay of a print control apparatus, and in particular, to a print control apparatus suitable for execution of a continuous printing operation while changing over between print formats.
2. Description of the Related Art
Heretofore, a print control apparatus of a printer using a continuous form accomplishes a successive printing of print data by use of an overlay operation of predetermined formats. In this operation, in order to enable the continuous printing even when change-over operations are achieved among a plurality of formats, the print control apparatus is provided with the formats stored in a format memory thereof. However, since the format memory is of limited capacity, thereof, the number of formats to be stored is accordingly restricted, and hence when this limit is exceeded, namely, when a format other than those stored in the format memory is used, a format replacement or change-over is necessary. Consequently, a processing wait state is required for the print control apparatus to change the format, which results in an interruption of the continuous printing.
As a prior art technology related to this kind of print control apparatus, there has been known technology described in the JP-A-60-22234, JP-A-57-58536, and the like. Referring now to the accompanying drawings, an example of the prior art technology will be described.
FIG. 1 shows a configuration of a print control apparatus according to the prior art technology, FIG. 2 is an explanatory diagram useful to explain states where page data are stored and read out in the conventional print control apparatus, and FIG. 3 is a schematic diagram showing an example of print results in relation to page data associated with a format change-over according to the prior art technology. The configuration of FIGS. 1-2 includes a channel adapter buffer 10, a page memory 11, a format entry 12, page data 13, a format memory 14, format data 15, dot expansion control sections 16-17, and a dot memory 18.
The print control apparatus according to the prior art technology comprises, as shown in FIG. 1, a channel adapter buffer 10 connected to channels of a host computer, a page memory 11 and a format memory 14 respectively storing page data 13 and format data 15 sent from the host computer linked to the channel adapter buffer 10, dot expansion sections 16-17 expanding into dot data the data respectively transmitted from the page memory 11 and the format memory 14, and a dot memory 18 storing the dot data received from the dot expansion sections 16-17.
Upon initiation of a print operation in the print control apparatus of FIG. 1, prior to transmission of print data, the host computer (not shown) sends a format address via the channel adapter buffer 10 to the page memory 11. The format address includes data indicating a format with which an overlay operation is to be achieved to print a page of print data to be transmitted later and is stored in a format entry 12 of the page memory 11. In the print control apparatus, a page of print data can be sequentially overlaid with a plurality of formats, thereby effecting data printing. Consequently, the host computer can transmit a plurality of format addresses associated with a page of print data, namely, the format entry 12 is configured to be capable of storing a plurality of format addresses.
When the format addresses are completely stored in the format entry 12, the host computer sends the format data 15 to the channel adapter buffer 10. The format data 15 is then fetched from the channel adapter buffer 10 so as to be stored at a location corresponding to the format address in the format memory 14.
Next, the host computer transmits print data to the channel adapter buffer 10. From the channel adapter buffer 10, the print data is fetched and is stored at a predetermined location of the page memory 11 in a page-by-page fashion. As a result, a page of the print data and the format address stored in the entry 12 are loaded as page data 13 in the page memory 11. When an operation to store a page of print data in the page memory 11 is finished as described above, the host computer stores a format address of the next page and print data in the format entry 12 and the page memory 11, respectively. In this operation, if a format to be overlaid is identical to that employed in an overlay operation on the print data of the previous page, the host computer stores only the print data in the page memory 11, so that the format address and format data are not re-transmitted. In this case, the format entry 12 associated with the print data of this page is loaded with a format address identical to that of the preceding page.
While the host computer is storing page data 13 in the page memory 11 as described above, if the page data 13 overflows the page memory 11, the new print data is written in areas of the page data 13 which have already been printed through a print operation (to be described later) beginning from an area thereof located nearest to the top of the page memory 11.
The page data 13 stored in the page memory 11 is printed as follows. Namely, the page data 13 stored in the page memory 11 and the format data 15 located in the format memory 14 indicated by a format address in the format entry 12 of the page data 13 are expanded in the dot representation by the dot expansion control sections 16 and 17, respectively and thereafter the resultant dot data are overlaid in the dot memory 18 for the storage and the dot data thus overlaid in the dot memory 18 are supplied to a printer.
Referring now to FIG. 2, description will be given of states where the page data 13 is stored and is read out at a certain point in the print control apparatus effecting the operation above.
In FIG. 2, it is assumed that page data 20 is already read out, that page data 21 (including page data 22, 23 and 24) has not been read out yet, page data 22 is being subjected to a dot expansion, that page data 23 contains the page data for the next page to be printed, and that page data 24 includes the latest page data stored in the page memory 11. In addition, a plurality of format addresses are assumed in be registered to the format entry 12 of the page data 22 currently being subjected to a dot expansion.
In the print control apparatus of FIG. 1, the print data of the page data 22 and the first format registered to the format entry 12 are overlaid in the dot memory 18, and the overlaid data is sent to the printer; thereafter, the next format registered to the format entry 12 is overlaid for the same print data. For the page data 22, when the last format registered to the format entry 12 is overlaid, the print control apparatus proceeds to processing of the next page data 23.
In a case where after the latest page data 24 is stored in the page memory 11, when storing print data of the next page, if format to be overlaid with the print data of the next page is missing from the format memory 14 and if no area for storing new format data is available in the format memory 14, the host computer will attempt to replace the stored format data with a new group of formats, including the format, to be used thereafter, in the format memory 14. The operation above is controlled in the print control apparatus as follows. After all page data is completely read out from the area of the page data 21, namely, upon completion of a print operation the data of a group of the new formats are stored in the format memory 14.
When the format change is finished, the host computer sequentially stores page data 13 associated with the format address and the print data in the page memory 11. The print control thereafter is accomplished such that the processing is restarted with the page data 24 for execution thereof.
FIG. 3 is a schematic diagram showing a processing example of the prior art, specifically, a print out operation in which the page data 22 and the format data 15 of FIG. 2 are processed according to the concrete print data and formats.
Format addresses 61-64 in the format entry 12 respectively correspond to format data 65-68, and the respective data are related to print forms shown in FIG. 3. The print data of the page data 22 is assumed to be a character string of "ABC". The diagrams 69-72 respectively represent results attained by overlaying the print data "ABC" with the format data 65-68.
As a result of the operation described in conjunction with FIG. 2, the overlaid results 69-72 are sequentially delivered to the printer, which then prints out the overlaid results 69-72 on the respective sheets of the print paper.
In the print control apparatus of the prior art, the format data must be frequently changed over and the transmission of dot data to the printer is interrupted while the format, data is being changed, which leads to a interruption of the print operation.